1. Field of the Invention
The invention relates generally to improvements in coupling devices, and more particularly, but not by way of limitation, to a coupling for the vibration-damping transmission of torques, comprising: an inner coupling member, which is provided with a substantially radial flange, and an annular outer coupling member, which surrounds the inner coupling member substantially concentrically, an annular toroidal compression cushion of elastomeric material, which is U-shaped in longitudinal section and which is connected to the outer coupling member along its outer edge and to the flange of the inner coupling member along its inner edge, an annular chamber being defined inside the compression cushion, and a plurality of non-extensible ropes, which are each connected to the outer and to the inner coupling members, in uniform distribution along the periphery of the coupling members, and are arranged substantially in longitudinal planes around the annular toroidal compression cushion, the compression cushion being loaded and resiliently deformed by compression through the ropes under the action of a torque to be transmitted, when the coupling members are rotated relative to each other from a position of rest.
2. Description of the Prior Art
A vibration-damping coupling of this general type is known from German patent specification 2 318 612.
In the prior art coupling the coupling members are annular bodies arranged concentric to each other, which are interconnected through a pair of toroidal compression cushions arranged on both sides of the annular bodies. The compression cushions consist of fluid-filled, non-extensible hulls of flexible fluid-tight material. They are generally toroidal, the center of the cross-sectional circle of the compression cushions being located at an axial distance, with respect to the coupling axis, from the annular bodies. In this way the compression cushions have substantially the shape corresponding to their maximum volume, when the coupling is in its state of rest. The hulls consist of rubber or the like with non-extensible ropes extending therearound embedded therein and affixed to the coupling members. With relative rotation of the coupling members under the action of a torque to be transmitted, there will be a relative angular offset of the points of attachment of the ropes to the inner and the outer coupling members. Due to this angular offset the loops formed by the ropes are shortened in axial direction. Thus, they exert pressure on the compression cushions, namely by compressive load through the ropes, whereby the volume of the fluid-filled hulls is varied. The compression cushions counteract this volume variation by an elastic resistance. In this way resilient and vibration-damping force transmission between the coupling members is achieved.
In these prior art couplings the compression cushions consist of fluid-filled hulls, preferably filled with compressed air. The resistance is caused by a volume variation, and thus by a pressure variation of the fluid enclosed in the hulls, accompanying relative rotation of the coupling members. This design requires filling of the hulls with fluid under well-defined pressure. This pressure, and thereby the stiffness of the coupling, may vary as a function of temperature. There is also the risk that the pressure may drop gradually due to leakage.
Furthermore, couplings are known in which coupling members are annular bodies arranged concentrically to each other, which are interconnected through annular toroidal rubber bodies. With rotation of a driving coupling member relative to a driven coupling member, the driving coupling member pulls at the rubber body in a peripheral direction. The tensile stress is then transmitted to the driven coupling member. Thereby the rubber bodies are subjected undesirably to tension and shearing, when the torques are transmitted. Such type of load impairs the torque transmitting capacity both of the toroidal rubber bodies and of the attachment of the rubber bodies to the driving and driven coupling members.